Means for adjusting reflectors



Aug. so, 1938. F. A. BENFOR'D 2,128,791

MEANS FOR ADJUSTING REFLECTORS Filed Sept. 15, 1936 Inventor: Frank A. Benford,

M 6 12%! 135 His Attorrfgg.

Patented Aug. so, 1938 mans roa amusma numerous Frank'A. Beniord, Schenectady, N. Y., assignor to General Electric Company, a corporation 01 New York Application September 15.1e3c,seriaiNc.'1oc,sc5

1 1 Elaim.

My invention relates to an adjusting and truing means for reflectors, more particularly for mirrors, used in light projectors.

One object of my invention is to provide an improved'and simplified means whereby the mirfror used in light projectors, such as searchlights,

(c1; ta-13) for example, may be readily adjusted to project I a true and symmetrically shaped beam.

For a better understanding of my invention, together with other and further objects thereof, reference is had to the following description, taken, in connection with the accompanying drawing, and its scope will be pointed out in the appended claim. r i In the accompanying drawing Fig. 1 illustrates a fragmentary view of the back of a searchlight drum provided with adjusting means built in accordance with my invention; Fig.2 is -a crosssectional view-illustrating the details of my improvedadjusting means; Fig. 3 illustrates a target showing the shape of a beam projected by a poorly adjusted and warped reflector,\and Fig. 4

illustrates the same beam projected subsequent to a truing of the reflector with the aid of my im proved adjusting and truing means.

Referring to the drawing in detail, Fig. l illus- "trates the fragmentary back view of a searchlight drum ill in which a series of set screws H are equa spaced near the edge of the drum, project t rough the wall of the drum and. are parallel to the axis of the drum. They-are provided with lock nuts H. .The set screws and lock nuts are both. operable from outside of the drum so that adjustments may be made when operating temperatures.

both the drum and mirror have reached normal In the example illusthrough line 2-2 of Fig. 1 looking in the direction of the arrows, isillustrated. In this figure a fragment of the mirror it provided with a reinforcing rim i4 is illustrated. This reflector is preferably made of metal, the surface of which is suitably treated and polished, to produce a face, or a seat, It for the back surface of the mirror rim It. The drum is further machined to provide a surface it for supporting the out- In Fig. 2 a section of this drum it, taken The curvature of this mir- 1' ror within the drum a ring-ibis provided which 9 sidesurface, or perimeter, of the rim it. A. gasket i1 is provided between the perimeter of rim M and the surface it to establish a snug fit between the drum and the rim. The mirror and drum herein illustrated are, for a -inch 5 diameter searchlight wherein a slight distortion of the reflectedbeam results in a substantial loss of the revealing power of this beam. A simple means for truing the reflector at any time during operation is,therefore, of considerable imv 10 porta'nce.

In order to properly adjust and clamp the mir is clamped against a machined surface it, which is parallel to surface it, by means of a suitable is number of bolts 20. The parallel surfaces are preferably at right angles to the axis of the drum and are spaced from each other .by a distance which is slightly greater than the thickness of the rim-M. In the ring it, directly opposite to and axially alined with each of the set screws ii, a plunger M is provided. This plunger is provided with a head 22 mounted in a cup 23 and is urged forward by a spring it. The plunger moves in and out of the cup 23 through a bearing, or/neck portion 25, and the pressure with which it is urged outwardly may be regulated by a cap 26 screwed into the end of the cup 23. In the illustrated example the cup 23 is attached to the ring by means of its neck por- 30 tion 25 which is peened over, welded-pr attached in any other suitable manner. It is, of course, 7 not necessary for ring it to be a solid ring. The same clamping action may be obtained by mounting the cups 23 into individual lugs which can 35 be bolted to the surface it by bolts 20 and which can be alined with the screws ll so that each plunger 2i and screw M will move on a common axis. The cross-section of ring it indicates a greater thickness under'the bolt head 29 than 40 in the several parts of the projector, or other 50 i causes occurring during the manufacture of either the drum and the reflector or during operation of the light. It becomes important, therefore, to provide means for adjusting the,

-rim of the reflector and thereby the mirror it- 56 metrical beam which in the present instance is a round beam. This may be readily accomplished with my improved adjusting means by first clamping the reflector in the drum, then -mounting the ring 68 and bolting it up against its seat to by means of the bolts 20. The plungers 242 then engage the rim. M and force it towards the surface t5 and against the ends of the set screws M. Then, if the beam proves to be distorted, its-becomes merely necessary to turn the set screws ti and thereby move the rim toward. or away from its seat to at the various points at which. the set screws and the opposing plunger hold the rim, until the true symmetrical beam is obtained. After this adjustment each set screw may be locked into position by the loch-nut it.

As stated above, the plungers 2t and set screws H are serially alincd so that their respective pressures on two swiaces of the mirror rim at any two corresponding points which are op poslte to each other are equal and opposite. Since set screws and plungers are aimed, in that they are arranged on a common axis. and since the set screws H are parallel to the axis at the drum, the corresponding opposite points on the two surfaces of the rim are the points through which this common axis is drawn. This is of considerable advantage because no local distortion is set up due to these two opposing forces. Thecorrecting distortion is onlyfoetween the points" of contact between the adjacent set screws and plungers.

A ready means for determining the shape of a projected beam is illustrated in Figs. 3 and i. Fig. 3 illustrates a chart 2'? having horizontal and vertical scale markings which intersect at the center of the chart. A chart of this type and of any suitable size may be set up at about 15o feet from a projector of this size and the beam projected thereon. In Fig. 3 the cross-section oi the beam'ls oval-shaped indicating a distorted mirror. The most convenient method of 'using my improved adjusting means is to advancethe set screws it beyond the surface I! so that the rim of the reflector will be spaced centrally between surface it and the inner surface of the ring 88. Adjustments may then be made in either a forward or reverse direction. In the case of the beam illustrated in Fig. 3, the rim section in the upper right-hand quadrant of the target is too far forward of the remaining portion of the rim. 'I'nerefore, by backing out the screws ll this portion of the rim and the reflector section attached thereto may be moved by the plunger-s until the cross-section becomes a true circle. Tue advantage of this adjusting means being that the plungers hold the reflector rim against the end of each set-screw. It is, therefore, only necessary to adjust each set-screw separateiy with a simple screw-driver until the proper beam crow-section is obtained and then loci; the screens into their respective posttlons.

What 31 claim as new and desire to secure by Letters Patent of the United States is:

in a light projector the combination of a drum closed at one end, a reflector, and means for supporting and adjusting the rim of said reflector comprising a pair of spaced parallel annular surfaces at the closed end in said drum, adjusting screws projecting through the end wall of said drum and through one of said parallel surfaces against one side ofthe rim of said mirror, and a ring attached to the other of said parallel surfaces and provided with spring operated ptuncers axial-lg aligned with said screws and projecting against the other side of said rim to respectively urge said rim against said adjusting screws whereby said mirror rim may be adjusted solely by said adjusting screws.

FRANK A BENFORD. 

